Electronic-First Publication or Single-Article Publication (SAP) means that an article is published as soon as it has completed the production cycle, i.e., after the page proofs are returned by the authors and prepared for electronic publication. Each article is published in its final form, including the final bibliographic citation. New articles are added daily to the online journal, with the date of posting being listed as the publication date of the article. At monthly intervals these articles are collected together to make up the printed issues.
Such articles are identified by volume number and a six-digit article number (instead of volume and page number), for example, Phys. Rev. C 60, 015809 (1999). This format allows articles to be fully citable as soon as they are published electronically, while maintaining the same identifier for both the electronic and print version.
The articles are listed in the Table of Contents and appear in the printed issue according to increasing article number and can therefore be located in the usual manner. Articles can also be located by volume and article number using the Volume/Article lookup.
Note that pages are numbered consecutively within each article, e.g., 015809-1, 015809-2, however, the hyphen and additional digits should not be used when citing or searching for the article.
The six digits in the article number are currently derived as follows: The first two digits correspond to the issue number, the next two are determined by article type and subject the last two are assigned according to the order of publication of the article, within that issue and subject area. This algorithm facilitates the shift to article-at-a-time publishing while maintaining the familiar delineations of volume, issue, and subject.
The following journals now use the six-digit article identifier: PRA [1], PRB [2], PRC [3], PRD [4], PRE [5], PRL [6], PRST-AB [7], and PRST-PER [8].
Links:
[1] http://scitation.aip.org/pra/artnum.jsp
[2] http://scitation.aip.org/prb/artnum.jsp
[3] http://scitation.aip.org/prc/artnum.jsp
[4] http://scitation.aip.org/prd/artnum.jsp
[5] http://scitation.aip.org/pre/artnum.jsp
[6] http://scitation.aip.org/prlo/artnum.jsp
[7] http://prst-ab.aps.org/help/artnum.html
[8] http://prst-per.aps.org/help/artnum.html